Seminar given by Hiroyuki Ito of the Department of Information and Communication Sciences, Faculty of Engineering, Kyoto Sangyo University to the Redwood Center for Theoretical Neuroscience at UC-Berkeley on March 24, 2008.
Precisely synchronized neuronal activity has been commonly observed in the mammalian visual pathway under a wide range of stimulus conditions. Analysis of this neural behavior has often assumed that synchronous firing is stationary and maintained throughout the period of visual stimulation. We tested this assumption by applying the method of Unitary Events Analysis to pairs of simultaneously recorded spike trains in the cat LGN that were stimulated with stationary spots of light. To evaluate the significance of synchronous spike events, we developed and applied a non-parametric bootstrap test. The analysis showed that 40% of single unit pairs displayed significant synchronous activity (unitary events). In many unit pairs, the unitary events were optimally characterized at a bin width of 1 ms, indicating neural synchrony having high temporal precision. Many cell pairs displayed significant modulation of synchrony that could not be predicted by the temporal modulation of firing rates. These findings demonstrate that stimulus-evoked synchronous activity within the LGN is highly dynamic, and is not well characterized by conventional methods of cross-correlation analysis.